Unable to make good his escape after the explosion, the robber was arrested and is now in hospital, police said.
The man was among the three robbers who came on a bike to loot the Baidyapur branch of the bank in West Bengal's Nadia district. The trio entered the bank, situated on NH 34, at around 1 pm and forced its workers into a room at gunpoint.
However, one of the workers managed to press the alarm which made the locals rush in, the police said.
The locals, who had given the trio the chase caught the injured robber and handed him to the police.
His accomplices were, however, nimble enough to force a man out of his motorbike and make good their escape, the police said.
The injured robber has been admitted to Ranaghat sub-division hospital under police custody and the bike they came in has been seized by the police.